Extraction installation for mineral extraction

ABSTRACT

An extraction machine for an extraction installation is disclosed. The extraction installation may have a chain having a first chain strand section with a first end and a second chain strand section with a second end. The first and second chain ends may be connectable to the extraction machine for moving the extraction machine. The extraction machine may have a first chain mount configured to be connected to the first chain strand section. The extraction machine may also have a second chain mount configured to be connected to the second chain strand section. In addition, the extraction machine may have a first pre-tensioning device for building up a pre-tensioning force acting on the first chain mount such that a pulling force acts on the first chain strand section in the direction of the second chain mount.

TECHNICAL FIELD

The present disclosure relates to an extraction machine. More particularly, the present disclosure relates to an extraction machine of an extraction installation for mineral extraction.

BACKGROUND

The present disclosure is based on an extraction installation and an extraction machine together with traction carriage according to DE 10 2006 027 955 A1 and DE 10 2007 053 206 A1. In the generic extraction installation, the chain ends of an endless drive chain for the extraction machine formed as a coal plow are arranged on a traction carriage. The traction carriage, via a resilient element as coupling device, designated as a damping device, is arranged movably to a limited degree against the restoring force of plate spring assemblies in a recess in the extraction body of the extraction machine.

For illustration, FIG. 5 schematically represents an extraction installation with an extraction machine. The extraction machine is connected to a plow chain via a resilient or damped traction carriage according to DE 10 2007 053 206 A1. The extraction machine 500 is preferably an extraction plow for extracting coal in an underground longwall. In order to move the extraction machine 500, a plow chain 501, which is respectively deflected on a chain wheel 502 or 503, is provided. Both chain wheels 502, 503 are mounted in drive or reversal stations (not shown further) and can preferably both be driven by means of a motor drive (likewise not shown). In the diagram according to FIG. 5, the extraction machine 500 travels, as indicated by the arrow F, in the direction of travel towards the left towards the chain wheel 502. The chain strand section 501A in the direction of travel in front of the extraction machine 500, therefore, forms the pulling chain strand section, and the chain strand section 501B forms the rearward chain strand section. Both chain strand sections 501A, 501B are fastened on a chain mount 505, which is common here, which is formed rigidly on a traction carriage 530. The traction carriage 530 is arranged movably within limits in a recess 520 in a machine body 506 of the extraction machine 500. Within a traction carriage housing 531, which is only schematically indicated here, there is arranged a spring 532. The spring 532 acts with both of its ends on plungers 533, which can move relative to the traction carriage housing 531 against the restoring force of the spring 532.

If a schematically indicated working face 508 is worked with the extraction machine 500, given a correspondingly high pre-tensioning of the spring 532, which for this purpose can consist for example of a plate spring assembly, it can be ensured that a damping effect is achieved in the normal operational behaviour of an extraction machine. The compression force of the spring 532 is for this purpose preferably greater than the tension force within the drive chain 501, since otherwise, just by virtue of the usually present chain tension of the drive chain 501 between both chain wheels 502, 503, the traction carriage housing 531 would be displaced laterally within the recess 520. The traction carriage housing 531 would be displaced laterally within the recess 520 in such a way that the housing section of the traction carriage housing 531, which is situated in each case towards the front in the direction of travel, would bear against the recess 520 and, in this respect, spring travel would no longer be available for the plunger 533. In the case of unfavourable operating states, as indicated in FIG. 5, chain sag may occur in the rearward chain section 501B, as indicated schematically in FIG. 5 and designated by reference sign 501B′.

The resilience of the coupling device, which is effective between traction carriage 530 and machine body 506, makes it possible, during a change in the direction of travel but also during blockages or other unfavourable operating states, to prevent an impact-like mutual abutting of the contact surfaces between traction carriage and extraction machine from occurring. The generic extraction installation with a corresponding traction carriage coupled via a resilient system has proved to be successful in underground mining, in particular in the extraction of coal, and has led to a considerable improvement in the service life and the operational behaviour of the extraction machine. During operation of such an extraction installation with resilient coupling device with respect to an extraction installation with a rigidly connected plow chain or rigidly connected traction carriage, it has moreover been shown that the vibrational behaviour of the pulling chain strand section is also improved. The pulling chain strand section is also improved since the vibration amplitudes in extraction installations with extraction machines rigidly connected to the chain turn out to be substantially greater than in extraction installations with a resilient coupling device on the traction carriage. This reduction in the vibrations contributes to the reduction in the vibration loading of the chain and also of the chain locks.

Since, in a corresponding manner to the longwall length of modern underground extraction operations, the length of the extraction installations has a tendency to become ever greater for economic reasons, the drive capacities and the dimensions of the chains used must also increase. As a result, the problem of the occurrence of so-called chain sag increases. Chain sag may occur in particular in that chain strand section, which, depending on the respective direction of travel of the extraction machine, is situated behind the extraction machine pulled by chain. To avoid chain sag, the prior art proposes tensionable drive or reversal stations by means of which the spacing of the two chain wheels from one another is changed, if appropriate also during active operation of the extraction machine, so as to counteract the occurrence of chain sag by the change of spacing.

In DE 10 2007 043 043 A1, sensor devices are arranged in the drive or reversal stations, by means of which sensor devices the chain state is detected, preferably both in the upper side and in the lower side of the chain, in order, depending on the chain state detected, either to change the speed of rotation of at least one drive motor or to change the extension state of a tensioning device in the drive or reversal stations, and as a result, to counteract the occurrence of chain sag or to avoid excessive chain tensions.

The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.

SUMMARY OF THE DISCLOSURE

According to an aspect of the present disclosure, an extraction machine for an extraction installation including a chain with first and second chain ends at respective first and second chain strand sections, the first and second chain ends being connectable to the extraction machine for moving the extraction machine, may comprise a first chain mount configured to be connected to the first chain strand section. The extraction machine may further comprise a second chain mount configured to be connected to the second chain strand section, and a first pre-tensioning device for building up a pre-tensioning force acting on the first chain mount such that a pulling force acts on the first chain strand section in the direction of the second chain mount.

According to another aspect of the present disclosure, an extraction installation for mineral extraction may comprise an extraction machine as exemplary disclosed herein.

According to yet another aspect of the present disclosure, a traction carriage for an extraction machine movable by means of a chain with first and second chain ends at respective first and second chain strand sections, may comprise a traction carriage body configured to be inserted into a recess in the extraction machine, the traction carriage body being provided with a first chain mount to which the first chain strand section is connectable. The traction carriage may further comprise a resilient device integrated into the traction carriage for both directions of movement. The first chain mount may be subjected by means of a first pre-tensioning device to a pre-tensioning force such that a pulling force acts on a first chain strand section in the direction of the second chain mount.

According to a further aspect of the present disclosure, an extraction installation for mineral extraction may comprise at least one extraction machine having a machine body, with a chain with two chain ends to which the extraction machine is connected via chain mounts, for moving the extraction machine, and with two chain wheels for driving and/or deflecting the chain into drive stations or deflection stations which receive the respective chain wheel. Both chain mounts may be subjected by means of at least one pre-tensioning device to a pre-tensioning force which exerts, on the chain strand section of the chain connected to the respective chain mount, a pulling force in the direction of that chain wheel around which the chain strand section connected to the other chain mount is deflected.

According to still another aspect of the present disclosure, an extraction machine for an extraction installation in particular as disclosed herein, may comprise a machine body and chain mounts to which a chain for moving the extraction machine can be connected. Both chain mounts may be subjected by means of at least one pre-tensioning device to a pre-tensioning force which exerts, on a chain strand section of the chain which can be connected or is connected to the respective chain mount, a pulling force in the direction of the other chain mount.

According to yet another aspect of the present disclosure, a traction carriage for an extraction machine as exemplary disclosed herein which can be moved back and forth by means of a chain, may comprise a traction carriage body which can be inserted into a recess in an extraction machine and which is provided with chain mounts to which a chain for moving the traction carriage body can be connected. A resilient device for both directions of movement may be integrated into the traction carriage. Both chain mounts on the traction carriage may be subjected by means of at least one pretensioning device to a pretensioning force which exerts, on a chain strand section of the chain which can be connected or is connected to the respective chain mount, a pulling force in the direction of the other chain mount.

Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and refinements of an extraction installation according to the present disclosure and of an extraction machine according to the present disclosure will emerge from the following description of exemplary embodiments shown schematically in the drawing. In the schematic drawings:

FIG. 1 shows, in a schematically highly simplified form, an extraction installation according to the present disclosure together with an extraction machine with a pre-tensioning device according to a first exemplary embodiment;

FIG. 2 shows an extraction installation together with an extraction machine with a pre-tensioning device according to a second exemplary embodiment;

FIG. 3 shows an extraction installation together with an extraction machine with a pre-tensioning device according to a third exemplary embodiment;

FIG. 4 shows an extraction installation together with an extraction machine with a traction carriage according to a further embodiment according to the present disclosure; and

FIG. 5 shows an extraction installation together with an extraction machine according to the prior art according to DE 10 2007 053 206 A1.

DETAILED DESCRIPTION

FIG. 1 illustrates, in a schematically highly simplified form, an extraction installation 10 according to a first exemplary embodiment.

An extraction machine 50 is moved along a working face 18 to be worked by means of a drive chain 1 which is deflected on a first chain wheel 2 and a second chain wheel 3. Both chain wheels 2, 3 are arranged within schematically indicated drive stations 15 which can be provided with drive motors (not shown) and, if appropriate, also with a tensioning device for changing the distance between the two chain wheels 2, 3. In modern extraction operations, the distance between both drive stations 15 may be, for example, 400 m and more, which leads to correspondingly high chain lengths of the drive chain 1.

In the schematic illustration according to FIG. 1, the extraction machine 50 moves in the direction of travel F towards the left-hand drive station 15 with the chain wheel 2. The chain strand section 1A situated between the extraction machine 50 and the chain wheel 2 forms the pulling chain strand section and the chain strand section 1B situated between the extraction machine 50 and the chain wheel 3 forms the rearward, non-pulling chain strand section. The chain strand section 1A is fastened on a first chain mount 8 on the extraction machine 50 and the chain strand section 1B is fastened on a second chain mount 9 on the extraction machine 50.

A pre-tensioning device 40, which here comprises at least one spring 41, is provided between the two chain mounts 8, 9, which can each move on their own account relative to a machine body 6 of the extraction machine 50. Both chain mounts 8, 9 may be guided movably on the machine body 6 in such a way that they can move substantially only parallel to the direction of travel F. In the exemplary embodiment of the extraction machine 50, the spring 41 forms a tension spring, which pushes together the two chain mounts 8, 9, if the chain strand sections 1A, 1B are not connected, to a minimum distance from one another. By connecting the chain strand section 1A to the one chain mount 8 and the chain strand section 1B to the other chain mount 9 and applying a chain tension in the entire chain 1 between both chain wheels 2, 3, for example, by corrective tensioning of one of the two chain wheels, the machine-side chain mounts 8, 9 are pulled apart while building up or increasing a pretension in the spring 40. The tensile force or spring force of the spring 41 of the pre-tensioning device 40 is preferably lower by, for example, a power of ten than the chain tensioning force between both chain wheels 2, 3 that is normally introduced into the chain 1. The chain tensioning force between both chain wheels 2, 3 may be, for example, approximately 500 kN. The pre-tensioning force of the completely tensioned spring 41 within the pre-tensioning device 40 may then be, for example, 50 kN, even if these are only exemplary reference values.

The larger chain tractive force has the effect that both chain mounts 8, 9, as indicated by dot-dash line in FIG. 1 for the chain mount 9, are pulled against two spaced-apart fixed mounts 11 and 12 on the machine body 6, with the result that a correspondingly high pre-tensioning force is built up in the spring 41. The fixed mounts 12, 13 limit the respective movement path of the chain mounts in the pulling direction of the respective pulling chain strand section 1A or 1B. In the normal operating state, the chain tractive force both in the pulling chain strand section 1A and in the rearward chain strand section 1B is, owing to the chain tensioning force, greater than the pre-tensioning force of the spring 41 produced by pulling apart the chain mounts.

Therefore, in the normal operating state, both chain mounts 8, 9 are situated in direct contact with the fixed mounts 11, 12 on the machine body 6. If, however, chain sag occurs in the rearward chain strand section 1B, as is indicated with the reference sign 1B′ in FIG. 1, the chain tractive force in the chain strand section 1B then falls, owing to the chain sag, below the pre-tensioning force of the spring 41 of the pre-tensioning device 40, which here is directed from the chain mount 9 in the direction of the chain mount 8 or the chain wheel 2 pulling the chain strand section 1A, with the result that the chain mount 9 moves in the direction of the chain wheel 2 or the respective other chain mount 8 with corrective tensioning of the chain sag 1B′, without further measures having to be taken. The pre-tensioning force of the pre-tensioning device 40 that acts between both chain mounts 8, 9 is therefore virtually inertia-free and automatically correctively tensions chain sag over the movement path of the two chain mounts 8, 9 with respect to one another if the chain sag state occurs.

FIG. 2 shows a second exemplary embodiment of an extraction installation 110 according to the present disclosure. Functionally identical components are provided with reference signs increased by 100. As in the case of the first exemplary embodiment, the drive chain 101 runs around between two chain wheels 102, 103 which are each mounted in drive stations 115 and are preferably provided with a separate motor drive.

The extraction machine 150, which is provided with suitable extracting tools in order to remove material on a working face 118 in both possible directions of travel, here comprises two machine bodies 106A, 106B, which are separated from one another and which, although having a suitably large distance from one another, are connected to one another substantially fixedly in terms of movement, as is indicated here via the coupling rod 135. The chain mount 108 situated at the front in the direction of travel in the representation according to FIG. 2 is situated on the machine body part 106A, while the rearwardly situated chain mount 109 is correspondingly situated on the other machine body part 106B. The chain mount 108 to which the pulling chain strand 101A is connected and also the chain mount 109 to which the rearward chain strand section 101B is connected are in each case movable with respect to the associated machine body part 106A, 106B, wherein a first pre-tensioning device 140A is arranged between the respective chain mount 108 and the machine body part 106A and a second pre-tensioning device 140B is arranged between the other machine body part 106B and the chain mount 109, via which pre-tensioning device a pre-tensioning force is introduced into the respective chain strand section 101A or 101B.

As in the case of the previous exemplary embodiment, each pre-tensioning device 140A or 140B in each case comprises at least one spring 141A or 141B. When the extraction machine 150 travels in the direction of travel F, the chain mount 108 preferably bears against an end stop on the machine body part 106A in which the spring 141A is charged or loaded with the maximum value of its pre-tensioning force. The same applies in the normal operating state for the chain mount 109, as indicated by dotted line in FIG. 2. In this starting position, the chain mount 108 is pre-tensioned by the spring force of the spring 141A in the direction of the other chain mount 109 and the chain wheel 103 situated behind it and the chain mount 109 is correspondingly pre-tensioned towards the chain mount 108 and the chain wheel 102. This pre-tensioning force in each case counteracting the chain tractive force in both chain strand sections.

If now, owing to chain sag (not indicated in FIG. 2), the chain tensioning force in the chain section 101B falls below the pre-tensioning force of the pre-tensioning device 140B, the spring force of the spring 141B then moves the chain mount 109 correspondingly towards the other chain mount 108, as is indicated in unbroken lines in FIG. 2, with the result that chain sag is correctively tensioned and therefore avoided. The greater the spacing is selected here between the two machine body parts 106A, 106B or the associated end stops, the greater the distance and hence the extent of chain sag which can be correctively tensioned is. It is sought here that the pre-tensioning device on the extraction machine 150 can correctively tension at least twice the distance by which the chain wheels 102, 103 can be moved apart by means of the chain tensioning device.

FIG. 3 schematically shows a third exemplary embodiment of an extraction installation 200 with a first chain wheel 202 and a second chain wheel 203 on which the drive chain 201 is deflected and correspondingly driven. As in the case of the previous exemplary embodiment, the extraction machine 215 has a first machine body part 206A and a second machine body part 206B. The chain mount 208 is connected fixedly in terms of movement to the machine body part 206A and the chain mount 209 is connected fixedly in terms of movement to the machine body part 206B.

The pre-tensioning device 240 again comprises at least one spring 241 which is arranged either directly between the machine mounts 208, 209, as illustrated, but also could be effectively arranged between the machine body parts 206A, 206B in a suitable manner. The movement path between both machine body parts 206A, 206B is preferably limited in such a way that the one machine body part 206A rigidly pulls the other machine body part 206B with it during the machine travel if the movement path is exhausted, and therefore a maximum predetermined spacing between both machine body parts is achieved.

Therefore, in the normal operating state, the two machine body parts 206A, 206B have their maximum spacing from one another, as represented by the dotted representation of the machine body part 206B in FIG. 3. If, however, chain sag occurs in the rearward chain strand section 201B, as indicated in FIG. 3 by 201B′, the pre-tensioning force of the spring 241 then acts directly and the spacing between the two machine body parts 206A, 206B together with the spacing between the two chain mounts 208, 209 is reduced in the rearward chain strand section in order to correctively tension the chain sag 201B′. Here too, the pre-tensioning force of the pre-tensioning device 240 is built up by the chain tension of the chain 201, which pulls apart the two chain mounts 208, 209 together with machine body parts 206A, 206B counter to the restoring force of the pre-tensioning device 240.

FIG. 4 shows a fourth exemplary embodiment of an extraction installation 300. Here, as a departure from the previous exemplary embodiments, the extraction machine 350, as in the case of the generic prior art, is connected via a traction carriage 330 to the drive chain 301 which is deflected on the chain wheels 302, 303 within the respective drive stations 315. The traction carriage 330 is seated movably in a recess 320 in the machine body 306 of the extraction machine 350 and is provided in a manner known per se with a resilient device 332 which acts on plungers 333 guided movably in the traction carriage housing 331.

The device 332 here comprises a spring system which interacts with the plungers 333 and which ensures an elastic coupling of the traction carriage 330 in the recess 320 in the machine body. Here, however, the chain mount 308 for the pulling chain strand 301A, when the extraction machine 350 moves in the direction of travel F, and the chain mount 309 for the rearward chain strand section 301B are not directly arranged on the machine body 306, but directly on the traction carriage housing 331, as schematically indicated in FIG. 4. A first pre-tensioning device 340A acts between the chain mount 308 and the traction carriage housing 331 and a second pre-tensioning device 340B acts between the chain mount 309 and the traction carriage housing 331, which pre-tensioning devices are functionally constructed here as in the exemplary embodiment according to FIG. 2.

The chain mounts 308, 309 are movable relative to the traction carriage housing 331. FIG. 4 shows the position of the chain mount 309 during corrective tensioning of chain sag since the spring 341B, which is provided to apply a pre-tensioning force to the chain mount 309, has moved the chain mount 309, with corrective tensioning of the chain sag, away from a fixed mount 312 on the traction carriage housing 331 in the direction of the other chain mount 308 or the chain wheel 302, which is pulling here. Therefore, by means of the path change of the chain mount 309, the chain sag 301B′, which otherwise occurs, as schematically indicated in FIG. 4, is correctively tensioned. By contrast, on the pulling side, the chain mount 308 bears against the fixed mount 311 on the traction carriage housing 331, for which reason the resilience of the device 332 (spring, plungers 333) can take effect in a conventional manner.

INDUSTRIAL APPLICABILITY

One object of the present disclosure is to improve the operational behaviour of an extraction installation or an extraction machine for such an extraction installation.

To achieve this object, in an extraction installation with an extraction machine pulled by means of a chain, such as, in particular, a coal plow, it is provided that both chain mounts are biased by means of at least one pre-tensioning device to a pre-tensioning force which exerts, on the chain strand section of the chain connected to the respective chain mount, a tensile force in the direction of that chain wheel around which the chain strand section connected to the other chain mount is deflected. In an extraction machine, it is correspondingly provided that both chain mounts are subjected by means of at least one pre-tensioning device to a pre-tensioning force which exerts, on a chain strand section of the chain which can be connected or is connected to the respective chain mount, a tensile force in the direction of the other chain mount.

The solution according to the present disclosure therefore makes provision, by means of the pre-tensioning device, for introducing into the chain strand sections on or via the chain mounts an additional pre-tensioning force, which causes a relative movement of the respective chain mount and which can act automatically in the event that a “chain sag” chain state could occur in order to reduce or avoid the chain sag by corrective tensioning via the pre-tensioning device introduced between the respective chain mount and chain strand section. Since in modern extraction installations the traction chain for the extraction machine is in any case clamped between the chain wheels, the pre-tensioning force of the pre-tensioning device may be built up at the same time by introducing the chain tension between the chain drives.

According to one embodiment, both chain mounts may be provided with their own pre-tensioning device for building up a pre-tensioning force. The pre-tensioning devices may be in each case arranged between the machine body of the extraction machine and the associated chain mount and both chain mounts may be movable relative to the machine body. The pre-tensioning device may have in particular springs which are positioned in such a way that the spring force of the tensioned pre-tensioning device counteracts the chain tractive force. If, for example, the drive train may be tensioned as usual by changing the spacing of the chain wheels from one another, this causes a positional change of the chain mounts relative to the machine body, while at the same time building up a pre-tensioning force or increasing (tensioning) the pre-tensioning force of the pre-tensioning device. If then the chain tractive force during operation within the rearward, non-pulling chain strand section on the non-pulling side of the extraction machine falls below the pre-tensioning force of the pre-tensioning device, it may act with corrective tensioning of the chain sag until force equilibrium prevails again. These conditions are reversed with each direction reversal of the extraction machine and the rearward chain is tensioned, by virtue of the stored pre-tensioning force, in each case with the minimum required tractive force from the extraction machine. In order to correctively tension the chain sag, use is then made of the available movement path of the chain mounts relative to the machine body.

The same effect may also be achieved if, according to an alternative embodiment, only one pre-tensioning device for building up a pre-tensioning force may be arranged between the two chain mounts, wherein both chain mounts may then be movable relative to the machine body.

In yet a further alternative embodiment, the extraction machine may have a machine body with at least two machine body parts which are arranged at a distance from one another and connected to one another fixedly in terms of movement, wherein in each case one of the chain mounts may be arranged on one of the two machine body parts, can be moved relative to the associated machine body part and may be provided with its own pre-tensioning device for building up a pre-tensioning force, which acts between the respective chain mount and the associated machine body part.

In all of the aforementioned embodiment variants, in operational use, the chain mounts may be guided movably in guides on the machine body parallel to the direction of movement of the extraction machine.

According to yet a further alternative embodiment, the extraction machine may have two machine body parts which can be moved relative to one another and which can be varied in their distance from one another, wherein the pre-tensioning device acts and may be arranged between the two machine body parts, which can be moved with respect to one another. It is particularly advantageous here, if by varying the distance, a restoring force may be built up or is built up in the pre-tensioning device and/or in a separate restoring device for the machine body parts.

The solution according to the present disclosure may be particularly advantageous if the machine body of the extraction machine may be indirectly connected to the chain via a traction carriage. The traction carriage may be provided with a resilient, in particular elastically resilient, device for both directions of movement of the extraction machine and may be inserted into a recess in the machine body. Both chain mounts together with pre-tensioning device(s) may be arranged on the traction carriage provided with the preferably elastically resilient device. By means of the resilient system installed in the traction carriage, it is then possible at the same time and in a manner known per se to prevent the occurrence of increased vibration amplitudes and to achieve a better profile of the motor currents and motor speeds of rotation of the drive motors used for driving the chain wheels. By means of the resilient system, resonant vibrations in the rearward chain strand section may be prevented when switching the motors on or off, and the pre-tensioning device may cause a change in position of the respective chain mount and thus a change in length of the chain strand section is also counteracted.

Also in the embodiment with a traction carriage, either both chain mounts may be provided with their own pre-tensioning device for building up a pre-tensioning force, wherein the pre-tensioning devices may be in each case arranged between a traction carriage housing and the associated chain mount. Both chain mounts can be moved relative to the traction carriage housing. Alternatively, a common pre-tensioning device for building up a pre-tensioning force may be arranged between the two chain mounts, wherein both chain mounts can be moved relative to a traction carriage housing. Here, too, it may be advantageous if the chain mounts may be guided movably in guides on the traction carriage housing, which are arranged so as to be oriented parallel to the direction of movement of the extraction machine.

In all of the embodiments, it may be preferable for the pre-tensioning device to comprise at least one spring and, if appropriate, for the pre-tensioning force of this spring to be built up by a change in position of the two chain mounts relative to one another. The adjustment travel of the chain mounts, in particular when correctively tensioning chain sag, may be detected, if appropriate, and may be used for installation control or drive control.

The above object may also achieved by a traction carriage for an extraction machine, which can be moved back and forth by means of a chain. The traction carriage may comprise a traction carriage body, which can be inserted into a recess in the extraction machine and which is provided with chain mounts to which a chain for moving the traction carriage body can be connected. A resilient device for both directions of movement may be integrated into the traction carriage, which device preferably may ensure an elastic coupling of the traction carriage and hence of the plow chain to the plow body, wherein it may be provided according to the present disclosure that both chain mounts on the traction carriage are subjected by means of at least one pre-tensioning device to a pre-tensioning force. The pre-tensioning force exerts, on a chain strand section of the chain which can be connected or is connected to the respective chain mount, a tensile force (pulling force) in the direction of the other chain mount.

Numerous modifications, which are intended to fall within the scope of protection of the following claims are obvious to a person skilled in the art from the preceding description. It will be understood that, with each direction reversal of the extraction machine, the conditions of the pulling chain strand section and of the rearward chain strand section are reversed and, correspondingly, with the occurrence of chain sag, the other chain mount would be moved away via the pre-tensioning device if the chain tractive force in the rearward chain strand section drops and chain sag could have occurred in this respect. The pre-tensioning device(s) on the extraction machine may be designed in such a way that they can correctively tension at least twice the distance by which the chain wheels can be moved apart by means of tensioning devices in the drive or reversal stations. Each pre-tensioning device may also have a plurality of springs or other devices for applying a pre-tensioning force. The resilient device in the traction carriage preferably comprises springs or spring systems such as a plate spring assembly in order to be able to withstand the high forces, which may occur. Instead of elastic (damping) systems with springs, it could also be possible to use purely hydraulic or pneumatic damping systems or combination systems with springs. One of the stations receiving the chain wheel may also form a driveless, preferably tensionable reversal station.

Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims. 

1. An extraction machine for an extraction installation including a chain having a first chain strand section with a first end and a second chain strand section with a second end, the first and second chain ends being connectable to the extraction machine for moving the extraction machine, the extraction machine comprising: a first chain mount configured to be connected to the first chain strand section; a second chain mount configured to be connected to the second chain strand section; and a first pre-tensioning device for building up a pre-tensioning force acting on the first chain mount such that a pulling force acts on the first chain strand section in the direction of the second chain mount.
 2. The extraction machine according to claim 1, wherein the first pre-tensioning device is further configured for building up a pre-tensioning force acting on the second chain mount such that a pulling force acts on the second chain strand section in the direction of the first chain mount.
 3. The extraction machine according to claim 1, further comprising: a machine body, wherein the first pre-tensioning device is arranged between the machine body and the first chain mount; a second pre-tensioning device for building up a pre-tensioning force acting on the second chain mount such that a pulling force acts on the second chain strand section in the direction of the first chain mount, wherein the second pre-tensioning device is arranged between the machine body and the second chain mount; and the first and second chain mounts are movable relative to the machine body.
 4. The extraction machine according to claim 1, further comprising: a machine body, wherein: the first pre-tensioning device is arranged between the first chain mount and the second chain mount; and the first and second chain mounts are movable relative to the machine body.
 5. The extraction machine according to claim 1, further comprising: a machine body including a first machine body part and a second machine body part arranged at a distance from one another and connected to one another fixedly; and a second pre-tensioning device for building up a pre-tensioning force acting between the second chain mount and the second machine body part such that a pulling force acts on the second chain strand section in the direction of the first chain mount, wherein: the first chain mount is arranged on the first machine body part and is movable relative to the first machine body part, the second chain mount is arranged on the second machine body part and is movable relative to the second machine body part; and the first pre-tensioning device is provided for building up a pre-tensioning force acting between the first chain mount and the first machine body part.
 6. The extraction machine according to claim 1, further comprising: a machine body, wherein in operational use, the first chain mount and the second chain mount are guided movably in guides on the machine body parallel to the direction of movement of the extraction machine.
 7. The extraction machine according to claim 1, further comprising: a machine body including a first machine body part and a second machine body part movable relative to one another, wherein the first pre-tensioning device acts and is arranged between the first machine body part and the second machine body part.
 8. The extraction machine according to claim 7, further configured such that by varying the distance a restoring force is adjustable in the pre-tensioning device and in a separate restoring device for the machine body parts.
 9. The extraction machine according to claim 1, further comprising: a machine body; a traction carriage inserted into a recess in the machine body and provided with a resilient device for both directions of movement of the extraction machine indirectly connectable to the chain via the traction carriage, wherein the first chain mount, the second chain mount, and the first pre-tensioning device are arranged on the traction carriage.
 10. The extraction machine according to claim 9, further comprising a second pre-tensioning device for building up a pre-tensioning force acting on the second chain mount such that a pulling force acts on the second chain strand section in the direction of the first chain mount, and the second pre-tensioning device is arranged on the traction carriage.
 11. The extraction machine according to claim 10, further comprising: a traction carriage housing for the traction carriage, wherein: the first pre-tensioning device is arranged between the traction carriage housing and the first chain mount; the second pre-tensioning device is arranged between the traction carriage housing and the second chain mount; and the first and second chain mounts are movable relative to the traction carriage housing.
 12. The extraction machine according to claim 1, wherein the first pre-tensioning device is arranged between the first chain mount and the second chain mount, wherein the first chain mount and the second chain mount are movable relative to a traction carriage housing for the traction carriage.
 13. The extraction machine according to claim 9, wherein the first chain mount and the second chain mount are guided movably in guides on a traction carriage housing for the traction carriage which, in operational use, are arranged so as to be oriented parallel to the direction of movement of the extraction machine.
 14. The extraction machine according to claim 1, wherein: the first pre-tensioning device comprises at least one spring; and the second pre-tensioning device comprises at least one spring.
 15. The extraction machine according to claim 1, wherein the adjustment travel of the first chain mount and the second chain mount is detected and useable for installation control or drive control.
 16. An extraction installation for mineral extraction, comprising: an extraction machine; a chain including: a first chain strand section having a first end; and a second chain strand section having a second end, the first and second chain ends being connectable to the extraction machine; a first chain mount connected to the first chain strand section; a second chain mount connected to the second chain strand section; and a first pre-tensioning device configured to generate a pre-tensioning force on the first chain mount such that a pulling force acts on the first chain strand section in the direction of the second chain mount.
 17. A traction carriage for an extraction machine movable by means of a chain with first and second chain ends at respective first and second chain strand sections, the traction carriage comprising: a traction carriage body configured to be inserted into a recess in the extraction machine, the traction carriage body being provided with a first chain mount to which the first chain strand section is connectable; and a resilient device integrated into the traction carriage for both directions of movement, wherein the first chain mount is subjected by means of a first pre-tensioning device to a pre-tensioning force such that a pulling force acts on a first chain strand section in the direction of the second chain mount.
 18. The traction carriage of claim 17, wherein the traction carriage body is further provided with a second chain mount to which the second chain strand section is connectable; and the second chain mount on the traction carriage is subjected by means of the first pre-tensioning device and a second pre-tensioning device to a pre-tensioning force such that a pulling force acts on the second chain strand section in the direction of the first chain mount.
 19. The extraction installation according to claim 16, further including: a machine body, wherein the first pre-tensioning device is arranged between the machine body and the first chain mount; and a second pre-tensioning device for generating a pre-tensioning force on the second chain mount such that a pulling force acts on the second chain strand section in the direction of the first chain mount, wherein: the second pre-tensioning device is arranged between the machine body and the second chain mount]; and the first and second chain mounts are movable relative to the machine body.
 20. The extraction installation according to claim 16, further including: a machine body; a traction carriage inserted into a recess in the machine body and provided with a resilient device for both directions of movement of the extraction machine indirectly connectable to the chain via the traction carriage, wherein the first chain mount, the second chain mount, and the first pre-tensioning device are arranged on the traction carriage. 